Oxidation of aromatic hydrocarbons to phenols with oxygen

ABSTRACT

An aromatic hydrocarbon having 6 to 18 carbons is oxidized to a phenol of the same number of carbons by contacting with oxygen, cuprous acetate, and acetic acid at 0* to 150* C.

United States Patent [191 Heck [ Feb. 27, 1973 [75] Inventor:

[ OXIDATION OF AROMATIC HYDROCARBONS TO PHENOLS WITH OXYGEN Richard F. Heck, Wilmington, Del.

[73] Assignee: Hercules Incorporated, Wilmington,

Del.

[22] Filed: May 22, 1968 [21] Appl. No.: 731,276

[52] U.S. CI ..260/621 G, 204/80, 260/397.5, 260/619 R, 260/619 F, 260/620, 260/624 R [51] Int. Cl. ..C07c 37/00 [58] Field of Search...260/621 G, 619 R, 619 F, 620, 260/624 R; 204/78, 86

[56] References Cited UNITED STATES PATENTS 3,397,226 8/1968 Fenton ..204/78 X FOREIGN PATENTS OR APPLICATIONS Allmand, Principles of Applied Electrochemistry, Edward Arnold, London (1912) pp. 245-248 TP255AL.

Primary Examiner-Bernard Helfin Assistant ExaminerNorman Morgenstern Attorney-John W. Whitson [5 7] ABSTRACT An aromatic hydrocarbon having 6 to 18 carbons is oxidized to a phenol of the same number of carbons by contacting with oxygen, cuprous acetate, and acetic acid at 0 to 150 C.

3 Claims, No Drawings OXIDATION OF AROMATIC I-IYDROCARBONS TO PHENOLS WITII OXYGEN ArI-I Cu H O Cu ArOH 2H wherein the water provides the oxygen for the phenol formation, and temperatures above about 175 C. are required for this.

It is also known to react benzene or toluene with oxygen in the presence of cuprous salts or cupric salts and metallic copper, the copper being freshly generated by chemical cleaning of a copper metal surface, or by generating copper metal in situ as by the first-mentioned reaction at high temperature in the presence of water. In this process, the copper becomes oxidized to copper oxide, and copper metal is regenerated by reduction of the copper oxide.

in accordance with the present invention, it has now been found that phenols are produced in an improved process by contacting an aromatic hydrocarbon having at least one replaceable hydrogen on the aromatic nucleus with cuprous acetate, oxygen, and acetic acid at a temperature in the range of to 175 C.

The process is represented by the following chemical reaction:

where Arl-l represents the aromatic hydrocarbon, ArOl-l the resulting phenol, and Ac represents the Cl-l CO group.

The aromatic hydrocarbons which are oxidized to phenols in the process of this invention are benzene, naphthalene, anthracene, diphenyl, dibenzyl, tetrahydronaphthalene, phenanthrene, indane, and alkyl derivatives thereof having up to 18 carbon atoms. The aromatic hydrocarbon must have at least one unsubstituted hydrogen on the aromatic nucleus. Examples of such hydrocarbons are: toluene, o-, m-, and pxylenes, durene, isodurene, mellitene, prehnitene, l,2,5trimethylnaphthalene, t-butylbenzene, and retene.

The cupric acetate produced by the oxidation process of this invention is converted back to cuprous acetate chemically or electrolytically within the acetic acid solution for reuse. It may also be converted back to cuprous acetate outside the reaction system.

The amount of cuprous acetate used is 5 to 20 percent of the weight of the reaction mixture.

The reaction mixture is a mixture of the hydrocarbon to be oxidized, and acetic acid of concentration from to 100 percent and containing 90 to 0 percent water. The amount of acetic acid is at least half the weight of the cuprous acetate which provides a mole of acetic acid for each mole of cuprous acetate. The ratio of hydrocarbon reagent to the acetic acid of concentration 10 to 100 percent is variable in the range of 20:1 to 1:20 by weight.

The oxygen may be introduced under pressure, or it may be maintained in the system at atmospheric pressure. Instead of oxygen, air or other oxygen-containing gas is useful. The pressure is not critical and may vary from atmospheric to 3,000 p.s.i.g.

The temperature for this reaction is any temperature in the range of 0 to 150 C. and is preferably in the range of 10 to 100 C.

The invention is illustrated by the following examples:

EXAMPLE 1 A solution of 2.46 g. cuprous acetate (0.02 mole) in a mixture of 10 ml. acetic acid (glacial) and 10 ml. benzene was stirred 16 hours at 25 C. with oxygen at 50 p.s.i.g. pressure. At the end of this time, the solution was 0.075 M in phenol. This is a 7.5 percent yield based on cuprous acetate.

EXAMPLE 2 A mixture of 5 ml. toluene and 15 ml. acetic acid (glacial) was stirred for 3 hours at 25 C. under 50 p.s.i.g. oxygen pressure with 2.46 g. cuprous acetate (0.02 mole). The resulting solution was 0.028 molar in o-cresol and 0.007 molar in p-cresol.

EXAMPLE 3 A mixture of 5 ml. toluene and 10 ml. acetic acid (glacial) and 5 ml. [-1 0 was stirred for 3 hours at 25 C. under 50 p.s.i.g. oxygen pressure with 2.46 g. cuprous acetate (0.02 mole). The resulting solution contained a trace of o-cresol.

EXAMPLE 4 A solution of 13 g. lithium acetate, 6.5 g. cupric acetate, 117 ml. acetic acid and 13 ml. toluene was placed in the cathode compartment of an electrolysis cell having a 250 ml. capacity. A platinum gauge cathode was placed in the cathode compartment around a 30 ml. Alundum cup which was filled with a solution of 2 g. lithium acetate in acetic acid, and a platinum anode of 2 sq. in. area was immersed in this solution. Oxygen gas was introduced into the cathode compartment under the anode as a fine stream of bubbles. The temperature of the contents was raised to C., and a current of 0.4 amperes was applied between the two electrodes. The emf was 0.02 to +0.05 volts. After 6 hours, the contents of the cathode compartment was neutralized with sodium bicarbonate and extracted with methylene chloride. The methylene chloride extract amounted to 12.2 g. which analyzed 15 percent o-cresol, 5.1 percent m-cresol, 5.4 percent pcresol, 7.9 percent o-tolyl acetate, 14 percent m-tolyl acetate containing some benzyl acetate and 4.8 percent p-tolyl acetate.

EXAMPLE 5 A mixture of 5 g. naphthalene in 15 ml. glacial acetic acid was stirred at 55 C. with 2.46 g. cuprous acetate (0.02 mole) under 50 p.s.i.g. oxygen pressure. After 2 hours, the solution contained 0.1 percent betanaphthol.

EXAMPLE 6 a. A mixture of ml. toluene and 15 ml. glacial acetic acid containing 20 millimoles cuprous acetate was heated at 100 C. with stirring with oxygen under 30 p.s.i.g. for 1 hour.

b. Another mixture of 5 ml. toluene and a mixture of 10 ml. glacial acetic and 5 ml. water containing 20 millimoles cuprous acetate was heated at 100 C. with stirring with oxygen under 30 p.s.i.g. for 1 hour.

c. Another mixture of 5 ml. toluene and a mixture of 5 ml. glacial acetic acid and 10 ml. water containing 20 millimoles cuprous acetate was heated at 100 C. with stirring with oxygen under 30 p.s.i.g. for 1 hour.

d. A mixture of 5 ml. toluene and a ml. water containing millimoles cuprous acetate dissolved therein was heated at 100 C. with stirring with oxygen under 30 p.s.i.g. for 1 hour.

Each of the resulting mixtures was analyzed, the toluene phase and the aqueous phase being analyzed separately for cresols and the results combined. The results were:

o-cresol m- & p-crcsol Total (a) Total Millimoles 0.620 0.180 0.80 (b) Total Millimoles 0.844 0.424 1.268 (c) Total Millimoles 0.378 0.226 0.604

(d) Total Millimoles trace trace What I claim and desire to protect by Letters Patent 1. A process for producing phenols which comprises intimately contacting an aromatic hydrocarbon having six to 18 carbon atoms and at least one nuclear hydrogen atom with oxygen and cuprous acetate at a temperature in the range of 0 to 150 C. and a pressure in the range from atmospheric to 3,000 p.s.i.g., said hydrocarbon and said cuprous acetate being in solution in acetic acid containing 0 to about percent by weight of water, and the amount of acetic acid being at least molecularly equal to the amount of cuprous acetate.

2. The process of claim 1 in which the aromatic hydrocarbon is benzene.

3. The process of claim 1 in which the aromatic hydrocarbon is toluene. 

2. The process of claim 1 in which the aromatic hydrocarbon is benzene.
 3. The process of claim 1 in which the aromatic hydrocarbon is toluene. 